Fix Exception in HystrixThreadPoolDefault.touchConfig() on Java 11

Java 11 ThreadPoolExecutor.setCorePoolSize() throws an IllegalArgumentException if the new coreSize is larger than the current maximumPoolSize.
Similarly, setMaximumPoolSize() throws an exception if the new value is less than the current coreSize.

Author: michaelnelson123

hystrix-core/src/main/java/com/netflix/hystrix/HystrixThreadPool.java

@@ -227,8 +227,18 @@ private void touchConfig() {
                             dynamicCoreSize + " and maximumSize = " + configuredMaximumSize + ".  Maximum size will be set to " +
                             dynamicMaximumSize + ", the coreSize value, since it must be equal to or greater than the coreSize value");
                 }
-                threadPool.setCorePoolSize(dynamicCoreSize);
-                threadPool.setMaximumPoolSize(dynamicMaximumSize);
+                // In JDK 11, setCorePoolSize will not allow a value greater than the current maximumPoolSize.
+                if (dynamicCoreSize <= threadPool.getMaximumPoolSize()) {
+                    threadPool.setCorePoolSize(dynamicCoreSize);
+                    threadPool.setMaximumPoolSize(dynamicMaximumSize);
+                } else {
+                    // In JDK 11, setMaximumPoolSize will not allow a value less than the current corePoolSize.
+                    if (dynamicMaximumSize < threadPool.getCorePoolSize()) {
+                        threadPool.setCorePoolSize(1);
+                    }
+                    threadPool.setMaximumPoolSize(dynamicMaximumSize);
+                    threadPool.setCorePoolSize(dynamicCoreSize);
+                }
             }
 
             threadPool.setKeepAliveTime(properties.keepAliveTimeMinutes().get(), TimeUnit.MINUTES);